This is topic 4KW rectifier with 3KW lamp in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Giorgio Volpi (Member # 1182) on 03-31-2006, 05:30 AM:
 
Hi,
a new customer of mine has a Strong Highlight consolle with a 100-150A rectifier. He used to use a 4KW lamp, but after theatre change is using a 3KW one. The lamp life is very short. Do you think is for the inappropriate rectifier or for any other reason?
Thanks in advance, Giorgio.
 

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Posted by Michael Schaffer (Member # 1204) on 03-31-2006, 06:41 AM:
 
Does that console have a switching (black box) or high reactance power supply? Whatever it is, the current needs to be throttled down to 85-90A for a 3k lamp. Running it at a higher current setting as for 4k will definitely mess it up fairly quickly.
The switching power supplies can be quickly and easily adjusted by either one or two trimpots (fine and coarse) which are either located on top or the side of the PS or may also be mounted on the side of the lamphouse, below the current meter.
The high reactance PS is adjusted by input tabs on the side. I believe older versions also had a dial switch for this, but I haven't worked with one of these, so someone else has to comment on this.
The next important step would be to identify which type and model of PS you have. The current can be read from the meter in the side of the lamphouse. But I wouldn't rely on this. Better check the current with a clampon ampmeter.
 

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Posted by Giorgio Volpi (Member # 1182) on 03-31-2006, 08:10 AM:
 
Thanks, Michael.
The console has a high reactance power supply. It is at the minimum regulation. When the lamp is on the ammeter shows 110A and when the lamp is hot it shows 100A. Never less than that.
 

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Posted by Richard Fowler (Member # 893) on 03-31-2006, 08:57 AM:
 
Giorgio,
since you at the low range of the power supply an option is to control incoming voltage via buck/boost transformers or a variac set. I have done this on locations powered by generators and one situation where the power varied +/- 20% during the day. The limitation would be increased current used.
 

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Posted by Louis Bornwasser (Member # 3063) on 03-31-2006, 09:01 AM:
 
Remember also that the "no load" or boost voltage must be accomodated as well. If you have reduced the current appropriately, you will probably be LOW on no load DC. Usually there is another tape on the low current secondary to get additional "no load" voltage. Louis
 

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Posted by Michael Schaffer (Member # 1204) on 03-31-2006, 04:16 PM:
 
But would this affect the ignition boost circuit? Like you said, that circuit feeds off the secondary coil of one of the phases. But Richard meant controlling the power coming into the PS. Since that would throttle the voltage by about 10%, the ignition boost should still be sufficient.
 

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Posted by Louis Bornwasser (Member # 3063) on 03-31-2006, 08:21 PM:
 
Many rectifiers (especially Christie) literally won't light at all after a couple hundred hours. The problem is that the voltage that is normal is nearly at the top end of the capacitor break-down voltage rating. When the current is lowered from 140 amps to 105 amps, then the no load voltage falls too far. You are lowering the current with the primary on the large transformer; the "boost" secondary falls too far. Louis
 

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Posted by Giorgio Volpi (Member # 1182) on 04-01-2006, 12:20 AM:
 
Thank you very much to all you.
Giorgio.
 

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Posted by Gordon McLeod (Member # 33) on 04-01-2006, 01:42 PM:
 
Often I have had to add an outboard boost supply circuit to them to light when the rectifier is turned way down Kniesley also has that issue
 

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Posted by Richard Fowler (Member # 893) on 04-02-2006, 01:51 PM:
 
Personally no problems using LPA type of rectifiers....more problems with Christie as Louis stated. Kneisley had a R-2924 boost kit as an accessory. My last order of that kit poor Betty came through since she had to call an independent engineer to verify that they had the parts to make our order
 

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Posted by Mark Gulbrandsen (Member # 72) on 04-02-2006, 09:46 PM:
 

quote: Louis Bornwasser

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Many rectifiers (especially Christie) literally won't light at all after a couple hundred hours. The problem is that the voltage that is normal is nearly at the top end of the capacitor break-down voltage rating. When the current is lowered from 140 amps to 105 amps, then the no load voltage falls too far.

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